A Mid-Brunhes Climatic Event: Long-Term Changes in Global Atmosphere and Ocean Circulation

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Abstract
A long-term climatic change 4.0 × 10 5 to 3.0 × 10 5 years ago is recorded in deep-sea sediments of the Angola and Canary basins in the eastern Atlantic Ocean. In the Angola Basin (Southern Hemisphere) the climatic signal shows a transition to more humid ("interglacial") conditions in equatorial Africa, and in the Canary Basin (Northern Hemisphere) to more "glacial" oceanic conditions. This trend is confirmed by comparison with all well-documented marine and continental records from various latitudes available; in the Northern Hemisphere, in the Atlantic north of 20°N, climate merged into more "glacial" conditions and in equatorial regions and in the Southern Hemisphere to more "interglacial" conditions. The data point to a more northern position of early Brunhes oceanic fronts and to an intensified atmosphere and ocean surface circulation in the Southern Hemisphere during that time, probably accompanied by a more zonal circulation in the Northern Hemisphere. The mid-Brunhes climatic change may have been forced by the orbital eccentricity cycle of 4.13 × 10 5 years.